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HOMESERVICE MANUALSHYUNDAI1990EXCEL BASE, 2D HATCHBACK, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGFUEL SYSTEMFUEL PRESSURE
1990 Hyundai Excel Base, 2D Hatchback, Automatic

Fuel Pressure

1990 Hyundai Excel Base, 2D Hatchback, AutomaticSECTION Fuel Pressure
  1. Release fuel pressure. See FUEL PRESSURE RELEASE in this article. Disconnect high pressure fuel hose from to delivery pipe (at fuel filter). See Fig 1 . Cover hose connection with rags to avoid spraying of fuel.
  2. Using the Fuel Pressure Gauge Adapter (09353-24200) , install the fuel pressure gauge to the fuel filter. See Fig 1 . Tighten bolt to 18-25 ft. lbs. (25-34 N.m). Reinstall the negative battery cable.
    Fig 1: Installing Fuel Pressure Gauge
    G122003Courtesy of HYUNDAI MOTOR CO.
  3. Start engine. Ensure no fuel leakage is present from the pressure gauge or connection. Disconnect vacuum hose from fuel pressure regulator and plug the hose end.
  4. Measure and record fuel pressure at idle. Reconnect vacuum hose and again measure and record fuel pressure. For fuel pressure specifications, see FUEL PUMP SPECIFICATIONS table. If measurements are not within specification, go to step 5). If measurements are okay, go to step 8).
    FUEL PUMP SPECIFICATIONS

    Application Pressure psi (kg/cm2 ) (1)
    Excel & Sonata 2.4L
    With Vacuum 39 (2.8)
    Without Vacuum 47-50 (3.3-3.5)
    Sonata 3.0L
    With Vacuum 38 (2.7)
    Without Vacuum 46-49 (3.2-3.4)
    (1) Fuel pump volume specification is not available from manufacturer.
  5. If fuel pressure is low, check the following items:
    • Restricted fuel filter.
    • Fuel leaking to the return side. This can be caused by poor seating of the valve in the fuel pressure regulator.
    • Low fuel pump discharge pressure.
  6. If fuel pressure is too high, check the following items:
    • Sticking valve in fuel pressure regulator.
    • Restricted or bent fuel return hose or pipe.
  7. If there is no difference in fuel pressure whether vacuum hose is connected or not, check the following:
    • Restricted/damaged vacuum hose or fitting.
    • Sticking or poor seating valve in fuel pressure regulator.
  8. Stop engine and ensure fuel pressure gauge reading does not drop. If fuel pressure drops slowly after engine is stopped, an injector is leaking. If fuel pressure drops immediately after engine is stopped, check valve inside fuel pump is not closed.
  9. After testing is completed, release fuel pressure. See FUEL PRESSURE RELEASE in this article. Disconnect the fuel pressure gauge from the adapter bolt. Ensure the hose connection is covered with a shop towel to prevent fuel spray. Remove adapter bolt and replace with original bolt. Apply battery voltage to fuel pump drive terminal. See Figure and Figure . Check for leaks.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.